The use of polyether fluids is well known in applications such as hydraulic fluids, brake fluids, cutting oils and motor oils where the synthetic ability to structure properties such as water miscibility, fire resistance, lubricant properties and extreme pressure resistance provides a competitive advantage over other fluids. The polyether oils in practical use comprise polyalkylene glycols and their end-capped monoethers, diethers, monoesters and diesters. They include polyalkylene oxide polyether homopolymer, copolymer and block copolymer and can be prepared principally by the anionic polymerization or copolymerization of oxiranes or epoxides and other cyclic ethers. Small or large molecule end-capping groups are added in the polymerization to modify the properties of the resultant polyether as appropriate for the selected application.
Basic catalysts are generally employed in the art for the production of polyethers from cyclic ethers such as oxiranes because anionic catalysis produces a product with a substantially smaller or narrower molecular weight distribution than the product produced by cationic polymerization using conventional Lewis acids. Lewis acids are intrinsically of higher activity leading to extensive chain transfer and cyclic formation reactions. Also, effective acid catalysts for cyclic ether polymerization or copolymerization including liquid super acids such as fuming sulfuric acid, fluorosulfonic acid or BF.sub.3 /promoter catalysts are difficult to handle and are more troublesome to dispose of in an environmentally acceptable manner.
These activity and environmental issues are of great concern for the production of tetrahydrofuran-containing polyethers which employ acid catalysts. Substantial efforts in the prior art have been devoted to resolving these issues by preventing cyclic formations and by employing solid acid catalysts.
U.S. Pat. No. 4,568,775 describes a two phase process for the polymerization of tetrahydrofuran or a mixture of tetrahydrofuran and other cyclic ethers in contact with a heteropolyacid catalyst having 0.1 to 15 mol of water per mol of heteropolyacid catalyst present in the catalyst phase. The polyether glycols prepared from the process are useful as starting material for the production of urethane. The process uses large volumes of catalyst in the two phase process.
U.S. Pat. No. 4,988,797 polymerizes oxetan and tetrahydrofuran (THF) in the presence of excess alcohol in contact with acid catalyst wherein the molar ratio of acid catalyst to hydroxyl groups is between 0.05:1 and 0.5:1. The invention is particularly directed to the polymerization of oxetanes.
U.S. Pat. No. 5,180,856 teaches the polymerization of THF and glycidyl ether in the presence of alkanoI to produce polyethers. Lewis acid catalyst is used such as boron trifluoride. The polymerization is carried out in the presence of 0.01-5 weight percent of Lewis acid catalyst. The products are useful as lubricants. The Lewis acid catalysts that are dissolved in the polyether-products have to be separated, destroyed and discarded as wastes.
U.S. Pat. No. 4,481,123 teaches the production of polyethers from THF and alpha alkylene oxides having an alkyl radical containing 8-24 carbon atoms. The polymerization is carried out in contact with Lewis acid catalyst. The polymerization can further include C.sub.1 -C.sub.4 epoxide and alcohol. The polyether products are useful as lubricants.
The object of the present invention is to produce polyethers that possess superior lubricant properties and are compatible with synthetic hydrocarbon motor oil and mineral oil.
Another object of the invention is to produce the foregoing oil-compatible polyesters using as a method heteropolyacid catalysis in a single phase in low concentration.
Yet a further object of the present invention is to produce block and/or random THF and epoxide copolymers that contain novel end groups and/or structural units to provide oil compatibility and superior lubricant properties.